Our research program of measurement of polypeptide hormones with radioimmunoassay and radioreceptor assay during the coming year will focus on a number of objectives. Growth Hormone: 1) A radioimmunoassay for canine GH has been established in this laboratory and will be applied to a number of studies of GH control in normal and uremic dogs; 2) A radioreceptor assay for human growth hormone of great sensitivity will be applied to a comparison of RIA of GH as secreted by human pituitaries in vitro. Earlier work would suggest that the receptor inactive GH recognized by RIA is not the product of peripheral metabolism of GH but is probably secreted by the pituitary. This will be studied by perifusion experiments with normal and neoplastic human pituitaries; 3) We will continue to screen sera of patients with short stature and high serum GH levels for evidence of production of biologically inactive GH; 4) GH receptors human tissues will be studied with the objective of development of quantitative methods for studying inherited and acquired differences in GH responsiveness. Prolactin: 1) Receptors in mammary glands will be studied to characterize the alteration in affinity which appears to occur as lactation continues in the rabbit; 2) A clinical study is in progress in attempt to discover whether pregnancy and birth control pills, both stimuli of lactotrophic hyperplasia, are factors in the development of prolactin secretion tumors; 3) We are systematically studying patients with hyperprolactinemia to develop criteria for distinguishing functional hypersecretion from prolactin secretion by microadenomata. Insulin and related Hormones: We are utilizing an insulin receptor assay in isolating somatomedin from human and amniotic fluid. We hope to use the isolated somatomedin for a radioreceptor of that peptide.